Pyrrol-3-yl sulfoxide

The action of phosphorus halides on pyrrolinones and related compounds offers an alternative route to chloropyrroles. Yields of around 60% of 2,5-dichloropyrroles were obtained in this way from N-substituted succinimides (82ZC126). Vilsmeier reaction of N-alkylsuccinimidals formed chlorinated pyrrole aldehydes in modest yields (90CJC791), and there are other examples [66YZ158 81H(15)547]. A useful synthesis of chloropyrrole-2-carboxylates employed the action of phosphorus pentachloride on pyrrolidin-2-one-5-carboxylates (40) (87CB45) (Scheme 15), and in a Pummerer-type reaction pyrrol-3-yl sulfoxides were transformed by thionyl chloride into chloropyrroles. Yields were increased to >80% by the use of oxalyl chloride (88JOC2634) (Scheme 15). 

Greenhouse and colleagues have reported the regiospecific introduction of chlorine atoms into the 2-position of pyrrol-3-yl and indol-3-yl sulfoxides using oxalyl chloride [213]. For example, the pyrrol-3-yl sulfoxide (276), on treatment with oxalyl chloride followed by m-chloroperbenzoic acid oxidation (1.1 eq), gives the 2-chloro-substituted product (277) in 83% yield (Scheme 5.91). 

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See also in sourсe #XX -- [ ]

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